Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
  • G03F7/032—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with binders
  • G03F7/035—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with binders the binders being polyurethanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/34—Esters containing nitrogen, e.g. N,N-dimethylaminoethyl (meth)acrylate
  • C08F220/343—Esters containing nitrogen, e.g. N,N-dimethylaminoethyl (meth)acrylate in the form of urethane links
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
  • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
  • C08F299/06—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyurethanes
  • C08F299/065—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyurethanes from polyurethanes with side or terminal unsaturations
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
  • C08G18/4263—Polycondensates having carboxylic or carbonic ester groups in the main chain containing carboxylic acid groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/67—Unsaturated compounds having active hydrogen
  • C08G18/68—Unsaturated polyesters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/81—Unsaturated isocyanates or isothiocyanates
  • C08G18/8141—Unsaturated isocyanates or isothiocyanates masked
  • C08G18/815—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen
  • C08G18/8158—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen with unsaturated compounds having only one group containing active hydrogen
  • C08G18/8175—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen with unsaturated compounds having only one group containing active hydrogen with esters of acrylic or alkylacrylic acid having only one group containing active hydrogen
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/28—Applying non-metallic protective coatings
  • H05K3/285—Permanent coating compositions
  • H05K3/287—Photosensitive compositions

Definitions

• This invention relates to solder mask coatings having improved performance characteristics, and, more particularly, it is concerned with aqueous alkaline developable, UV curable urethane acrylate compounds and compositions useful for making such coatings.
• Sullivan in U.S. Patent 4,506,004, describes a contact method of imaging a liquid solder mask coating on a printed circuit board.
• the UV curable solder mask coating is screen printed to a given thickness, prehardened and imaged by exposure with suitable UV energy.
• the desired characteristics of good electrical performance and excellent printing resolution are given as the attributes of the Sullivan system.
• the requirements of a suitable photopolymerizable compound for use in this process include an ability to form a smooth, flexible coating which can impart chemical and heat resistance to the solder mask.
• the coating must exhibit excellent adhesion to the board, and an ability to be cured to a desired depth with a minimum of UV energy.
• solder mask coating is an ability to be developed with an aqueous, slightly alkaline solution, thereby avoiding the use of organic solvents in the developing step.
• the solder mask coatings also should exhibit flexibility, heat and chemical resistance, surface hardness, abrasion resistance, adhesion to the underlying metal of the printed circuit board, and a high cure depth at low dosages. These stringent requirements imply that the structure of the prepolymer and its formulation must be carefully designed before the solder mask can achieve commercial acceptability.
• This invention provides a UV curable, aqueous alkaline developable urethane acrylate compound for formulation into a composition useful in making a solder mask coating.
• the urethane acrylate compound of the invention is obtained by reacting (i) at least one diisocyanate compound selected from the group consisting of aliphatic and cycloaliphatic diisocyanates, e.g. dicyclohexylmethylene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate, (ii) one mole of a hydroxyalkyl acrylate; e.g.
• hydroxypropyl acrylate (iii) a polyol having at least 3 hydroxyl groups, e.g. glycerol; and (iv) at least one mole of a dicarboxylic acid anhydride, saturated or unsaturated, e.g. maleic anhydride.
• the urethane acrylate compound of the invention is characterized by the following: (a) terminal ethylenic unsaturation; (b) at least one terminal carboxylic acid group; and (c) alkylene connecting groups intermediate said terminal groups, one of which is preferably substituted with at least one hydroxy group.
• this invention provides a UV curable, aqueous alkaline developable urethane acrylate solder mask composition comprising:
• composition also may include about 1-5% by weight of one or more of the following: a cross-linking agent, a pigment or dye, a rheology modifier, and a thermal stabilizer; and 1-15% by weight of a filler.
• a feature of the invention is the provision of a printed circuit board having a cured solder mask coating thereon which can be screen printed to form a smooth, uniform, glossy, flexible coating.
• This solder mask coating can be cured at a low energy level to provide a high cure depth and excellent surface hardness, and abrasion, heat and organic solvent resistance.
• the coating can be developed rapidly in an aqueous, slightly alkaline medium at room temperature.
• Another feature of the invention is the provision of a UV curable urethane acrylate compound having a high degree of terminal ethylenic unsaturation per unit weight, which enables curing to take place at low energy levels.
• the compound has at least one terminal carboxylic group so that the cured coating can be developed rapidly in an aqueous, slightly alkaline medium.
• the compound is further characterized by the presence of an alkylene connecting group intermediate the terminal groups, which is preferably substituted with a hydroxyl group, which increases the aqueous solubility of the compound.
• the UV curable, aqueous alkaline developable urethane acrylate compound can be obtained by a three-step, two-part reaction sequence, the first step of which involves reacting a suitable diisocyanate compound with one mole of a hydroxyalkylacrylate to form the corresponding isocyanate-capped acrylate.
• Suitable diisocyanates for use in this step including aliphatic and cycloaliphatic diisocyanates, e.g. dicyclohexylmethylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanates, and trimethylhexamethylene diisocyanate.
• Aromatic diisocyanates are not preferred because they form non-flexible coatings.
• the hydroxyalkyl acrylate reactant may be selected from such compounds as hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and the like, although other acrylates known in the art may be used as well.
• acrylate includes the corresponding "methacrylate” derivatives.
• the second step in the reaction sequence is esterification of a suitable polyol reactant with a dicarboxylic acid anhydride to form an ester of the dicarboxylic acid.
• Suitable polyols have at least three, and up to six, hydroxyl groups in the molecule, and include such compounds as glycerol, trimethylolpropane, 1,2,6-hexanetriol, caprolactone polyol, and sugars, such as fructose. Glycerol is preferred.
• part of the polyol may include a suitable sulfur-containing diol, e.g. dihydroxydiphenylsulfone or the corresponding sulfide.
• Suitable dicarboxylic acid anhydrides for this step include such acid anhydrides as maleic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, phthalic anhydride and the like. Maleic anhydride is preferred.
• succinic anhydride succinic anhydride
• glutaric anhydride glutaric anhydride
• adipic anhydride phthalic anhydride and the like.
• Maleic anhydride is preferred.
• one mole of the acid anhydride is used, thus forming the monoester intermediate, and leaving two hydroxyl groups available for subsequent reaction.
• One hydroxyl group then will be substituted on the alkylene group in the final product.
• the corresponding diesters also may be prepared by using two moles of the acid anhydride, in which case two terminal carboxylic acid groups will be present in the final compound.
• the third and final step in the process is the condensation of the isocyanate-capped acrylate with the ester of the dicarboxylic acid anhydride.
• the final reaction is characterized by terminal ethylenic unsaturation at one end, and at least one terminal carboxylic acid group at the other end, with the organic diisocyanate moiety attached to the unsaturated group, and a alkylene group adjacent said terminal acid group.
• a hydroxyl group is present as a substituent on the alkylene group.
• Two terminal carboxylic acid groups also may be included in the final compound.
• the desired urethane acrylate may be prepared by a three-step, one-pot synthesis wherein the four reactants are added sequentially in the same reaction vessel. In this method, the diisocyanate is charged and the hydroxyalkyl acrylate is added slowly. After an initial reaction between these reactants, the polyol is added, followed by the dicarboxylic acid anhydride.
• R 2 is alkylene; dicarboxylic acid anhydride
• R 3 is alkylene
• R 4 is aliphatic or cycloaliphatic, saturated or unsaturated, or aromatic
• This invention also provides a UV curable, aqueous alkaline developable urethane acrylate composition for forming a soldering mask comprising: a) 40-70% by weight of (i) a urethane acrylate compound which is obtained by reacting substantially equal molar quantities of an aliphatic or cycloaliphatic diisocyanate and a hydroxyalkyl acrylate, with a polyol having at least three hydroxyl groups, and at least one mole of a dicarboxylic acid anhydride per mole of said polyol; or (ii) a mixture of 20-99% by weight of the urethane acrylate and 1-80% by weight of a urethane diacrylate; b) 20-50% by weight of a reactive monomer diluent; c) 0.5-10% of a photoinitiator; and d) 0-8% by weight of a triphenylphosphite.
• the reactive diluent monomers are added to the urethane acrylates of the invention to reduce its viscosity in the composition, and increase the curing rate.
• Suitable reactive diluent monomers for use herein include ethylenically unsaturated monomers that are compatible and copolymerizable with the substituted urethane acrylates of the invention.
• Such ethylenically unsaturated monomers include mono-, di- and tri-acrylates as, for example, hydroxyalkyl acrylates, such as e.g. hydroxyethyl acrylate; and acrylate esters, e.g.
• Suitable triacrylates include glycerol triacrylate, ethoxylated trimethylol triacrylate, and the like.
• reactive compounds can be included in the composition of the invention to increase the cross-linking density of the coating.
• Such reactive compounds include, but are not limited to, pentaerythritol 3-mercaptopro-pionate, 1,4-butylene dimethacrylate or acrylate, 1,1,6,-6-tetrahydroperfluorohexanediol diacrylate, ethylene dimethacrylate, glycerol diacrylate or methacrylate, glycerol trimethacrylate, diallyl phthalate and 1,3,5-tri(2-methacryloxyethyl)-s-triazine.
• the UV curable composition also contains a photoinitiator which generates free radicals owing to actinic light.
• Suitable examples of such photoinitiators include substituted and unsubstituted polynuclear quinones, such as 2-ethylanthraquinone, 2-t-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-diphenylanthra ⁇ quinone, thioxanthone, .e.g.
• ketoaldonyl compounds such, as diacetyl, benzyl and the like; ⁇ -ketoaldonyl alcohols and ethers, such as benzoin, pivalone, and the like; ⁇ -hydrocarbon-substituted aromatic acyloins such as ⁇ - phenylbenzoin, ⁇ , ⁇ -diethoxyacetophenone, and the like; and aromatic ketones such as benzophenone, 4 ,4'-bisdialkylaminobenzophenone, and the like.
• photoinitiators may be used alone or as a combination of two or more of them.
• Examples of combinations include 2,4,5-triarylimidazole dimer and 2-mercaptobenzoquinazole, leucocrystal violet, tris (4-diethylamino-2-methylphenyl)methane, or the like, and compounds which may not have photoinitiating properties alone but which nevertheless can constitute a good photoinitiating system, in combination with the above-mentioned materials.
• Such compounds include, for example, tertiary amines, such as triethanolamine and the like, which are used in combination with benzophenone.
• These photoinitiators and/or photoinitiator systems preferably are present in an amount of about 0.5 to 10% by weight of the composition.
• the urethane diacrylate compound is obtained by reacting (i) at least one diioscyanate compound selected from the group consisting of aliphatic, cycloaliphatic and diisocyanates, e.g. dicyclohexyl methylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and toluene diisocyanate, with (ii) two moles of a hydroxyalkyl acrylate, e.g. hydroxypropyl acrylate.
• diioscyanate compound selected from the group consisting of aliphatic, cycloaliphatic and diisocyanates, e.g. dicyclohexyl methylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and toluene diisocyanate
• the urethane acrylate component of the mixture of UV curable compounds provides flexibility characteristics, aqueous alkaline developability, adhesion, surface hardness, and high cure depth at a low energy level; while the urethane diacrylate provides enhanced electrical insulation resistance.
• the triphenylphosphite is present in an effective amount, suitably about 0.1 to 8% by weight of the composition, preferably about 0.4 to 5%, and, optimally, about 3%.
• the triphenylphosphite additive in the composition of the invention provides a cure depth of at least 18 mils at an energy level of 0.2 J/cm 2 .
• composition with triphenylphosphite is further characterized by stability toward gelation for long periods of time, and the retention of the other desirable properties of a commercial solder mask composition.
• the product was a viscous liquid having a Brookfield viscosity of 64,000 cps at 25°C., and an acid group contents of 1.48 meq/gm.
• a resin kettle equipped with a mechanical stirrer, thermometer, drying tube and pressure equalizing dropping funnel was charged with (A), (B) and (D). The mixture then was stirred while (C) was added slowly over 20 min. The temperature was maintained at below 55°C. Upon completion of the addition, the mixture was maintained at 55°-60°C. until the NCO number was 10.7 ⁇ 0.3, as determined by titration. (E) then was added slowly over 30 min. and the temperature was maintained at below 55°C. Heating was continued at 60°C. until IR showed the absence of NCO absorption at 2275 cm -1 . (F) then was added to the reaction mixture at 70-75°C. over 20 min., followed by (G). Heating was continued at 75°C. until the maleic anhydride was completely reacted, as indicated by the absence of peaks at 1845 and 1975 cm -1 .
• the product was a viscous liquid having a Brookfield viscosity of 320,000 cps at 25°C., and an acid group contents of 2.60 meq/gm.
• a resin kettle, equipped with a mechanical stirrer, thermometer, drying tube and pressure equalizing dropping funnel was charged with (A), (B) and (D). The mixture was stirred while (C) was added slowly over 20 min. The temperature was maintained at below 55°C. Upon completion of the addition, the mixture was maintained at 55°-60°C until the NCO number was 10.7 ⁇ 0.3 as determined by titration.
• a thermometer and drying tube was charged with (E), (F) and (G). The mixture was heated with stirring at 90°C. until the maleic anhydride was completely reacted, as indicated by the absence of peaks at 1845 and 1975 cm -1 .
• composition was prepared using the urethane acrylate of Example 1, and then used in forming a solder mask for a printed circuit board.
• Tone-100 (Union Carbide) reactive diluent monomer 25 .5 Pentaerythritol 3-mercaptopropionate- cross-linker 3 . 0
• Colloid 640 (Colloid Chem.) leveling agent 0. 8
• This composition is thixotropic with a Brookfield viscosity of 208,000 cps at 25°C at 0.5 rpm. and 39,200 cps at 100 rpm., and is stable without gelations for more than 6 months.
• Toluene diisocyante (1 mole) and hydroxypropyl acrylate (2 moles) are reacted at 550°C. for 6 hrs. to give the product, which was a viscous liquid having a Brookfield viscosity of 100,000 cps at 25°C.
• the following composition was prepared using a UV curable mixture of equal weight quantities of the urethane acrylate of Example 1, and the urethane diacrylate of Example 5.
• the composition was used in forming a solder mask composition for a printed circuit board.
• CAB-O-SIL thixotropic agent 4 Cymel 301 (Am. Cyan.) - cross-linker 5
• IRG 651 (Ciba-Geigy) photoinitiator 2
• Colloid 640 (Colloid Chem.) leveling agent 0.8 MTBHQ - mono-tert. -butyl hydroquinone-stabilizer 0.2
• This composition is thixotropic with a Brookfield viscosity of 208,000 cps at 25°C at 0.5 rpm. and 39,200 cps at 100 rpm., and is stable without gelation for more than 6 months.
• Example 7
• Example 1 A copper-clad epoxy fiber glass printed circuit board was cleaned by scrubbing to remove corrosion and foreign material, coated by screen printing with the above composition of Example 1 to a thickness of about 3 mils. Then a similar 3 mil thick coating was applied on a photo tool in accordance with the method given in U.S. 4,506,004, Example
• the two coatings then were given a flash curing with about 0.2-0.4 joules per cm 2 of energy using a mercury vapor lamp, to effect partial hardening.
• the two coatings were then mated to form a composite of 6 mils thickness, flipped over and given a main exposure with 0.5 joules per cm 2 for
• the cured solder mask exhibited the following performance characteristics: a smooth, uniform, glossy, and flexible coating having 100% adhesion under a cross-hatch tape test both before and after application of solder, resistance to organic solvents of greater than 15 minutes by immersion test; excellent legend ink adhesion characteristics; excellent heat resistance as measured by a 20-second dip in solder at a temperature of 260°C. without blistering; very good surface hardness and abrasion resistance; and excellent adhesion to the printed circuit board.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Macromonomer-Based Addition Polymer (AREA)

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• 1986
  • 1986-05-07 DE DE8686903785T patent/DE3676054D1/de not_active Expired - Fee Related
  • 1986-05-07 WO PCT/US1986/001012 patent/WO1986006730A1/en active IP Right Grant
  • 1986-05-07 EP EP86903785A patent/EP0222878B1/de not_active Expired
  • 1986-05-07 AU AU59057/86A patent/AU597257B2/en not_active Ceased
  • 1986-05-16 PH PH33782A patent/PH23679A/en unknown
  • 1986-05-16 CA CA000509364A patent/CA1255692A/en not_active Expired

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